The theoretical and empirical basis for a rule-learning model of serial-pattern learning that assumes functionally analogous capacities for humans and animals is examined. First, the model assumes that animals (namely, rats) and humans are sensitive to the ordinal or interval characteristics of stimulus sets, or "alphabets." Second, the model assumes that animals and humans are sensitive to the formal structure of serial patterns built from such an "alphabet." Evidence that supports these assumptions is presented, then evidence is reviewed that supports the idea that rats, like humans, can generalize and extrapolate abstract rule-structures, and that they can use cognitively demanding hierarchical rule-structures to learn serial patterns. The general goals of the proposed studies are to document the extent of rats' sensitivity to hierarchical structure in serial patterns and to characterize some of the factors that affect rats' capacity to detect, encode, and use information about pattern structure in learning serial patterns. Toward this end we will document rats' response to patterns having highly-organized hierarchical structure, to patterns having less completely nested structures, and to patterns containing structure that can be detected only if the rat is able to relate items that are not adjacent in the sequence. Finally, we will characterize some of the factors that contribute to detecting pattern structure and tracking the pattern. Specifically, we will determine the importance of phrasing cues, other temporal cues, and spatial cues for pattern tracking. We anticipate that this methodology will allow us to characterize rat sequential learning with the same precision that has been achieved in studying human sequential learning, and that from this work will emerge an animal model that can be used in guiding future work on neurobiological correlates of cognitive processes. Such a model would be useful for the areas of behavioral neuroscience, behavioral pharmacology, and behavioral toxicology. The resulting psychological model will contribute to our general understanding of animal cognitive capacity.